Literature References: Residue left after distilling off the volatile oil from the oleoresin obtained from Pinus palustris and other species of Pinus, Pinaceae. Offered as wood rosin (from Southern pine stumps), gum rosin (the exudate from incisions in the living tree, P. palustris and P. caribaea), and tall oil rosin, see Tall Oil. Rosin is chiefly produced in the U.S.A. Constit. About 90% resin acids and 10% neutral matter. Of the resin acids about 90% are isomeric with abietic acid (C20H30O2); the other 10% is a mixture of dihydroabietic acid (C20H32O2) and dehydroabietic acid (C20H28O2).